1. Field of the Invention
The present invention generally relates to a process and apparatus for the filling of a gas chamber of a piston-cylinder unit, for example a shock absorber, with compressed gas, and for closing this gas chamber with a closing element in the form of a base.
2. Background Information
European Patent Application No. 0 411 362 discloses a piston-cylinder unit in which an opening is made in the wall of the cylinder and the piston-cylinder unit is filled with a compressed gas medium via this opening. The opening is subsequently welded shut. The disadvantage of this process and/or unit is that only a relatively small opening is available. Accordingly, the filling process can essentially only proceed slowly. Furthermore, there is a reduction in the wall thickness which determines the pressure level inside the gas chamber.
German Patent Application No. 12 67 472 discloses a piston-cylinder unit which has a separate base which includes a filling opening. A piston-cylinder unit with a separate base can be manufactured under more favorable conditions than a piston-cylinder unit in which the cylinder and the base are realized as an integral unit, such as that disclosed in European Patent Application 0 411 362. However, there is reason to doubt whether a reliable seal can be realized by means of a caulking tool.
German Patent Application No. 24 55 901 also discloses an apparatus for closing a gas chamber in which gas filling takes place via the cylinder, the cylinder being open on one end of the piston-cylinder unit. The disadvantage of this type and manner of closure is the beading of the cylinder with a sealing element. If one imagines that the piston-cylinder unit is realized as a McPherson strut unit which must transfer torque via a drop arm on the cylinder, for example, this beading appears unsuitable since it is essentially unable to transfer torque. Another disadvantage is the disproportionately thick base, which in a shock absorber can negatively influence the unsprung weight.